Conventional scanning system can be approximately divided into two segments that are handy scanning system and flat-bed scanning system. A scanning system makes use of focusing a reflecting light beam through a photo detector to generate an image signal for further image processing. A conventional scanning system apparatus includes a light source, a mirror, and a lens set, which are used to guide the reflecting light to a charge couple device (CCD). The charge couple device is utilized to generate an image signal. Typically, image capture is achieved by passing the document in front of a device known as a CCD. This consists of a large of very small, individual semiconductor receptors, disposed in a linear array. The document is passed in front of the CCD and a complete image of the document linear segments individually captured from the CCD. A preprocessing element is used to respond an image signal and adjust dc gain of the image signal. An analogue to digital converter is used to convert adjusted image signal to a digital signal and a post-processing element to generate an image code by processing said digital signal through highlight, shadow, and Gamma correction.
Alignment is an important step for setting up a scanning system. In general, it needs an alignment pad 10 for the alignment, as shown in FIG. 1. The alignment pad 10 includes a set of black patterns 12 for boundary alignment. The boundary alignment is used to determine whether the area scanned by a CCD is in desired area or not. The height of the alignment pad 10 is used for horizontal alignment. The horizontal alignment can determine whether the line scanned by the CCD is horizontal or not. The resolution of a lens is determined by a plurality of vertical lines 14 on the alignment pad 10. The alignment signals is responsive to an oscilloscope, and the signals are displayed, analyzed on it. However, it is very hard to achieve exact results of the CCD and the lens by analyzing the alignment signal on the oscilloscope. By using the conventional alignment method, the horizontal resolution, vertical resolution, and magnifying power of the lens can not be achieve. Further, the boundary alignment and the resolution analysis can not be done at the same time. Thus, it is a hard task to align the CCD, lens by using the conventional method.
Therefore, what is required is a method for alignment the CCD and lens for a scanning system.